Heating unit manufacture



April 14, 1964 c. F. LOUTHAN 3,129,401

HEATING UNIT MANUFACTURE Original Filed Nov. 14, 1957 2 Sheets-Sheet 1 INVENTOR. C'keszer [10111 1 BY f WM HIS ATTORNEY April 14, 1964 c. F. LOUTHAN 3,129,401

HEATING UNIT MANUFACTURE Original Filed Nov. 14, 1957 2 Sheets-Sheet 2 INVENTOR.

CJexfer ff 1011291112! W HIS ATTORNEY United States Patent 3,129,401 HEATING UNIT IVJIANUFACTURE Chester F. Louthan, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Web, a corporation of Delaware Original application Nov. 14, 1957, Ser. No. 696,414, now Patent No. 3,082,511, dated Mar. 26, 1963. Divided and this application Nov. 13, 1961, Ser. No. 151,987 3 Claims. (Cl. 338-273) This invention relates to tubular sheath electric heating units that are commonly used as surface heaters for electric ranges and the like and more particularly to a method and apparatus for manufacturing these heating units. This is a division of my copending application Serial No. 696,414, filed November 14, 1957, now Patent No. 3,082,511.

An object of this invention is to provide a method and apparatus for manufacturing a tubular sheath heating element of the type having a tubular sheath containing one or more heating elements and a quantity of compacted finely divided electrical insulating material, and wherein the use of the method and apparatus of this invention results in a high degree of compacting of the finely divided material and also results in a finished product wherein the heating element or elements are spaced a predetermined distance from the tubular sheath along the entire length of the sheath and irrespective of the fact that the sheath may have been initially bowed. The foregoing object is preferably accomplished by supporting the tubular sheath in a vertical position and threading a heating element through the tubular sheath and through a tamping or spacer plug that is located within the tubular sheath and which has certain of its edges in contact with the internal walls of the tubular sheath. The tubular sheath is then supplied with a quantity of finely divided insulating material, such as magnesium oxide, and at the same time the tubular sheath is vibrated along the longitudinal vertical axis to cause vertical reciprocation of the spacer or tamping plug. At each reciprocation of the tamping plug, a quantity of insulating material passes around the plug and is compacted by the downward stroke of the tamping plug. During this vertical reciprocation, the tamping plug climbs in increments from the bottom of the tubular sheath to the top thereof and highly compacts the finely divided insulating material during its movement. The tamping plug in its movement follows the contour of the tubular sheath and thus correctly spaces the electrical heating element from the tubular sheath, the spacing being the same over the entire length of the tubular sheath.

It is another object of this invention to provide an end connection for a plurality of heating element wires wherein one end of one of the heating elements is folded over another to form a heating element cluster and wherein the cluster is forced into a tapered opening formed in a supporting plug, the heating elements being threaded through said opening except for the cluster which is tightly engaged by the walls of the tapered opening.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a pre ferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a vertical plan view with parts broken away of a heating element filling machine made in accordance with this invention;

FIGURE 2 is a sectional view taken along line 2--2 of FIGURE 1;

FIGURE 3 is an enlarged view of a portion of FIGURE 1 showing a method of supporting one end of a heating element;

FEGURE 4 is a sectional view taken along line 4--4 of FIGURE 1;

FIGURE 5 is a vertical sectional view of apparatus f0- filling a tubular sheath heating element wherein the heating unit contains a plurality of heating elements;

FIGURE 6 is a sectional view taken along line 6-6 of FIGURE 5;

FIGURE 7 is a sectional View taken along line 7-7 of FIGURE 5;

FIGURE 8 shows one step of making an end connection having a plurality of heating elements; and

FIGURE 9 illustrates a second step of forming an end connection having a plurality of heating elements.

. Referring now to the drawings and more particularly to FIGURE 1, the heating element filling machine of this invention comprises a main frame 11B that includes vertically extending side frame members 12 and 14. The side frame members 12 and 14 are connected by a cross member 16 which is bolted to the side frame and which has an opening 1% that is adapted to receive a metal tubular sheath 211 that forms a component part of a heating unit. The side frames 12 and 14 carry a plurality of reinforcing blocks 22 that are formed with vertically extending openings 24 that are aligned with openings 26 formed in the side frames. The openings 24 and 26 form guides for a vertically movable heating element supporting frame generally designated by reference numeral 28.

The vertically movable frame 23 includes a supporting block 3% which carries vertically extending parts 32 having studs 34 that are threaded into threaded openings in block 30. The heating supporting frame 23 further includes a cross member 36 that is held in fixed relation to blocks 32 by means of screws 38 which may be tightened to bear against blocks 32 and which provide an adjustable connection between the cross member 36 and blocks 32. The block 36 is provided with an opening 40 that is adapted to receive a supporting rod 42 and also has a set screw 43 that engages the rod 42 to hold it in fixed relationship with the cross member 36. The cross member 36 carries rods 44 that fit within the slots 24 and 26. The block 30 carries similar rods 46 that slide within vertical openings 24 and 2s. The rods 44 and 46 are thus contained within slots 24 and 26 and this arrangement prevents the frame 28 from rotating during vertical reciprocation thereof.

The filling machine of this invention has an impact vibrator 47 that may be either air operated or electrically operated and which operates to vertically reciprocate a block 43 having a recess 49. The block 48 is prevented from rotating by a guide 59 that is suitably attached to side frame 14. A similar block (not shown) may be disposed on the opposite side of vibrating block 48 in order to prevent the block 43 from rotating during its vibratory reciprocating movement. The vibrator 47 is preferably mounted in fixed relationship to the main frame of the machine by means (not shown). Where the frame is floor mounted, the vibrating mechanism 47 may also be floor mounted, and as noted above, the vibrator 47 may be air operated and may take the form of an air-hammer.

When it is desired to fill a tubular sheath heating unit, a tubular metal member 2% is fitted with a Wire coil heating or resistance element 52 that is welded or otherwise secured to metal rod terminals 53 and 54. In setting up the machine for a filling operation, a metal thimble 55 is threaded over the heating element and terminal 54 to a point where the thimble engages projections 56 formed integrally with the terminal 54. The thimble has a central opening as illustrated in FIGURE 1 through which the heating element 52 and terminal 54 are threaded.

the lower end of rod 42 by providing a reduced portion 60 on the rod 53 which fits within a slot 61 formed in the supporting rod 42. The terminal 53 is detachably connected to the lower end of rod 42 by simply slipping the end of terminal 53 into the openings formed in the rod 42 with the large diameter portion 63 of the terminal fitting over the annular portion 64 of rod 42. This connection between rod 42 and terminal 53 may be made after threading the heating element 52 through the tamping rod 57, and when the supporting rod 42 and heating element 52 are threaded therethrough, the rod may be fixed in place by the set screw 43. 7

When the tamping 'rod 57 and heating element 52 have been threaded through the tubular sheath 20, the sheath is positioned in the machine and the set screw 65 is tightened to hold the tubular sheath 20 in fixed relationship with cross member 30. In this position, the

lower end of tubular sheath 2% rests on the lower wall of recess 49 and a process fitting generally designated by reference numeral 66 and shown in detail in FIGURE 2 may then be attached to the tubular sheath 2t). The process fitting as shown in FIGURE 2 includes blocks 67 and 68 having arcuate recesses that are adapted to engage the outer periphery of tube 20. The blocks 67 and 68 are held together by threaded fasteners 69 which may be loosened or completely unthreaded to remove the process fitting from the position shown in FIGURE 1. The process fitting in its position in the machine lies directly on the vertically vibrating member 48 and the vertical reciprocation of the vibrating member 48 is transferred to the tube 2% through the process fitting 66.

The cross member 30 carries a hopper 70 having a conduit portion 71 of predetermined cross sectional area. The hopper is adapted to contain a quantity of finely divided insulating material, such as magnesium oxide. The insulating material is fed through chute 71 into an opening 72 formed in block 30 which communicates with the space between tamping rod 57 and tubular sheath 20. The chute 71 may be provided with any suitable valve mechanism for controlling the flow of magnesium oxide into the tubular sheath 2% and may be designed to feed any desired quantity of magnesium oxide into tubular sheath 29 for a predetermined or given period of time.

A weight member 73 is secured to the upper end of tamping rod 57 by means of a set screw as shown in FIGURE 1. The weight member 73 slidably engages one side of a guide member 73a that is fixed to frame 28, thus preventing rotation of the tamping rod 51 during reciprocation thereof. This weight provides for extra downtical reciprocation, the tamping rod 57 is vertically reciprocated within the tubular sheath 20 and simultaneously with this vertical reciprocation magnesium oxide is fed ,between the tamping rod 57 and the tubular sheath 20.

The magnesium oxide powder passes between theedges 58 of tamping rod 57 and the tubular sheath 2%, and starts to fill up the tube 263. This magnesium oxide is desigreciprocation moves upwardly within the tubular sheath 20, the tamping rod climbing slightly upwardly during each singular vertical reciprocation. Since the vibrator '47 is operated relatively rapidly, the tamping rod climbs up within tubular sheath 20 in small increments, as long as the vibrator 47 is in operation. The tamping rod 57 will thus move from the lower end of tubular sheath 20 to the top end thereof and when the tamping rod reaches the top end the tubular sheath 20 will'be completely filled with compacted magnesium oxide.

7 It is to be noted'that the tamping rod serves another function in that it spaces the heating element 52 away from the inner wall of tubular sheath 20 during its upward vibratory movement The tamping rod due to the engagement of edges 59 with tubular sheath 2.0 follows the contour of the tubular sheath 29 and thus insures that the heating element 52 will be spaced a predetermined distance from the tubular sheath 20 regardless of the fact that the tube 20 might be slightly bowed. It is also to be noted that the heating element 52 is neither tensioned nor slackened during the vibratory movement of ends of the heating element 52 to insure that it is neither.

tensioned nor slackened. V w

The apparatus shown in FIGURE 1 may also be used to fill a tubular sheath heating unit of the type illustrated in FIGURE 5 wherein the finished product contains three heatin elements that are spaced from one another by predetermined distances. In the embodiment shown in FIGURE 5 a metal tube 76 has a circular cross section except for a portion 77 that is flattened. In the embodiment bfFIGURE 5, a plug 78 is provided which has a tapered opening 80 that is of smaller diameter adjacent its top end thereof. The plug 78 has a shoulder 82 which is adapted to engage one end of the flattened portion 77 of the tube 76 when the plug is inserted therein. The

plug is preferably formed of crushable ceramic material throughplug 7S and passed over the looped end 35 of heating element 83. With the heating elements in the position shown in FIGURE 8, the end of heating element 84 is bent over the looped end of heating element 83 in a manner depicted in FIGURE 9. In this position of the heating elements 83 and 84, a heating element cluster is formed which is pulled into the tapered opening 80 and which tightly engages the side walls of the opening 80. It has been found that, by forming the'bunch or cluster as illustrated in FIGURE 9, a tight connection may be made'with plug 78 which supports the lower end of the heating elements within the tubular sheath 76.

When the heating elements 83 and 84 have beensecured to the plug 78 in a manner shown in FIGURES 8 and 9, and when the heating elements 83 and 84 have been positioned in the plug 78, the three terminal ends 86, 87 and 88 of the two heating elements are threaded through openings 8611,8711, and 88a formed in a tamping plug or spacer plug 89. The plug 89 has a fiat side 90 that is adapted to cooperate with the flat side 77 of tubular sheath 76 to prevent rotation of'plug 39 during vertical reciprocation thereof. The plug 39 is attached to a rod 91 which in turn carries a weight 92 that is fixed to the rod by means of a set screw 93. The terminal ends 86, 87 and 88 of the heating elements are connected with terminals 93 which fit within openings 94 formed in a fitting 95 that is carried by the upper end of tubular sheath 76. The fitting has set screws 96 which engage the terminals 93 to hold the terminals in fixed relationship with the tubular sheath 7 6. The fitting 95 has an opening that accommodates the rod 91 and has openings 99 which permit the passage of magnesium oxide therethrough during vertical reciprocation of the tamping plug 89. A filler chute member 97 may also be fitted to the fitting 95 in a manner shown in FIGURE 5 to provide for guiding means for the magnesium oxide insulating material.

As noted hereinbefore the machine shown in FIGURE 1 is useful in filling tubular sheath heating units of the type illustrated in FIGURE 5. In filling the unit of FIGURE 5,, the tubular sheath 76 is secured to the process fitting 66 shown in FIGURE 1, and the upper end of the tubular sheath 76 is fixed to the cross member 30 in a manner similar to the securing of tubular sheath 20 to cross member 30 and process fitting 66. The chute 71 is disposed to overlie the chute 97 whereby the hopper 70 is adapted to feed magnesium oxide into the chute 97. When the tube 76 of FIGURE 5 is inserted within the machine shown in FIGURE 1, the tube 76 is vibrated along its longitudinal axis to produce a longitudinal vibration of tamping plug 89, rod 91 and weight 92. The tamping plug 89 and its associated parts climb upwardly within the tubular sheath 76 in a manner similar to the climbing up of tamping rod 57 within tubular sheath 20. In the apparatus of FIGURE 5, the three heating elements 86, 87 and 88 are held at predetermined distances from one another and from the tubular sheath 76 due to the fact that they are threaded through the openings in spacer or tamping plug 89. The magnesium oxide represented by reference numeral 98 is compacted during the vertical reciprocation of tamping plug 89 to form a highly compacted mass within tubular sheath 76. It will be apparent that the operation of the apparatus shown in FIGURE 5 and in FIGURE 1 is substantially identical, the difference being that three heating elements are being positioned within the tubular sheath in FIG- URE 5 whereas in FIGURE 1 only a single heating element is being fitted within the tubular sheath.

When the tamping rod 89 has moved from the lower end of tubular sheath 76 to the top end thereof, the tube is completely filled and an end cap (not shown) may then be attached to the lower end thereof. The tube is then removed from the machine and may be swaged to crush the crushable member 78, the material of member 78 being thus highly compacted to hold the ends of heating elements 86, 87 and 88 together and from moving along the length of tubular sheath 76.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted as may come within the scope of the claims which follow.

What is claimed is as follows:

1. The method of holding a plurality of independent heating elements and a plug with a tapered opening in a tubular sheath prior to filling the sheath with a finely divided insulating material comprising, threading said heating elements through the tapered opening of said plug, folding one end of one of said heating elements over the other, pulling said folded over end of said one heating element and said other heating element into tight engagement with the narrow end of said tapered opening whereby said heating elements are electrically engaged, placing said plug within one end of said tubular sheath and in contact therewith, retaining said plug in said tubular sheath through the tight engagement of said heating elements with said plug, and holding the opposite ends of said heating elements in fixed relation with said tubular sheath.

2. In combination with a tubular heating element having two uninsulated Wire resistance elements therein, an end connection for said two uninsulated wire resistance elements, a tubular sheath surrounding said wire resistance elements and having a deformity, a plug having a tapered opening and a protuberance, said plug being insertible within said sheath until said protuberance engages said deformity, said wire resistance elements being threaded through said opening and being bunched together into electrical engagement by the contact with the narrow end of said tapered opening thereby to hold said protuberance against said deformity and to electrically connect said wire resistance elements.

3. In combination with a tubular heating element, a tubular sheath having a flattened portion, a plug for closing one end of said tubular sheath, said plug having a tapered opening and a shoulder portion engageable with said flattened portion to limit the movement of said plug interiorly of said sheath, said tapered opening having its smaller diameter directed toward the interior of said sheath, a first uninsulated wire resistance element in said tubular sheath and formed with a looped end in said tapered opening, a second uninsulated wire resistance element in said tubular sheath and having one end thereof bent over said looped end in said tapered opening, whereby said smaller diameter of said tapered opening compresses said first and second resistance elements into electrical engagement and effects a tight connection of said resistance elements with said plug to hold said plug in said sheath.

References Cited in the file of this patent UNITED STATES PATENTS 1,001,054 Lawrence Aug. 22, 1911 2,166,807 Ewald July 18, 1939 2,761,115 Visconti Aug. 28, 1956 

1. THE METHOD OF HOLDING A PLURALITY OF INDEPENDENT HEATING ELEMENTS AND A PLUG WITH A TAPERED OPENING IN A TUBULAR SHEATH PRIOR TO FILLING THE SHEATH WITH A FINELY DIVIDED INSULATING MATERIAL COMPRISING, THREADING SAID HEATING ELEMENTS THROUGHT THE TAPERED OPENING OF SAID PLUG, FOLDING ONE END OF ONE OF SAID HEATING ELEMENTS OVER THE OTHER, PULLING SAID FOLDED OVER END OF SAID ONE HEATING ELEMENT AND SAID OTHER HEATING ELEMENT INTO TIGHT ENGAGEMENT WITH THE NARROW END OF SAID TAPERED OPENING WHEREBY SAID HEATING ELEMENTS ARE ELECTRICALLY ENGAGED, PLACING SAID PLUG WITHIN ONE END OF SAID TUBULAR SHEATH AND IN CONTACT THEREWITH, RETAINING SAID PLUG IN SAID TUBULAR SHEATH THROUGH THE TIGHT ENGAGEMENT OF SAID HEATING ELEMENTS WITH SAID PLUG, AND HOLDING THE OPPOSITE ENDS OF SAID HEATING ELEMENTS IN FIXED RELATION WITH SAID TUBULAR SHEATH. 